This invention relates to a countermeasure system for protecting jet aircraft from detection by infrared detection systems. More particularly, this invention concerns itself with a high temperature, low reflectance coating system which, when applied to the strategic surfaces of aircraft jet engine components, will effectively reduce the level of emitted energy radiating from the aircraft and render it undetectable by airborne and ground-base infrared detection systems.
Tactical aircraft are prime targets for a variety of infrared seeking missiles and other infrared detection devices. These aircraft are especially vulnerable to air launched missiles while cruising at altitude or during a low level attack. In close support missions, they are vulnerable to ground launched missiles, such as Redeye, which are capable of providing an effective defense against low flying attacking aircraft. The low cost, ease of operation and high reliability of infrared seeking missiles make them an effective threat in all categories of military tatics where aircraft are utilized.
The missile's attack capability to seek out and destroy tactical aircraft could be nullified if the intensity of the jet engine radiation could be decreased in the missile's wavelength and bandwidth of response and the emitted radiation from the engine could be shifted to wavelengths outside of the response range of the missile's detectors. In the last analysis, the reduction of an aircraft's infrared signature requires a combined effort which includes both the incorporation of an efficient cooled exhaust system and the application of an optically, chemically and mechanically stable emissive/reflective coating to the surfaces of jet engine components.
For application to aircraft using advanced jet engines, and particularly for countermeasure purposes, a judicious selection of low reflectance and low emissivity surfaces on critical engine components is required to optimize the trade-off between emission and reflection. Also, the air-breathing environment limits the utilization of previously known coatings designed for thermal control of space oriented countermeasure coating systems. The severe environmental conditions encountered during the operation of a jet engine aircraft include the influences of high temperature stress, overtemperature, erosion, impact by foreign objects and the metallurgical instability of coatings.
As a consequence, a research effort evolved in an attempt to solve the problems encountered by prior art coating systems by providing a low reflective, high temperature, camouflage, coating system which, when applied to the strategic surfaces of jet engine aircraft, will reduce effectively their level of emitted energy and render them undetectable from infrared detection devices. The diminution should be restricted to the 1 to 6 micron wavelength region while the bulk of the radiation in the other wavelength regions should be allowed to propagate freely from the aircraft.
It was found that the problems referred to above could be overcome by the application of a coating system which comprised a glass-ceramic coating having ferrous sulfide as an essential additive ingredient. The coating of this invention overcomes the problems of mechanical instability and lack of mechanical strength that was exhibited by prior art camouflage coatings. Further, the present invention provides a coating that gives emittance values greater than those obtained heretofore. The distinct advantages of mechanical and chemical stability exhibited by this invention favor the use of this coating system as an infrared suppression coating for jet engine aircraft.